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holy_calamity writes "French physicists have built a desktop particle accelerator. It uses a pair of laser beams to precisely control the acceleration of electrons within a plasma. It has the power of a device that usually takes up a whole room and could lead to new medical treatments. They don't mention the potential for experiments like 'what happens if I put my lunch in front of a 300 megaelectronvolt beam?'"

No it hasn't. That's why the French team's work has appeared in the top journal Nature this week. The editor has written a freely accessible summary [nature.com] with links to the research article. The first paragraph [nature.com] of that is freely available.

A 300MEV beam signifies the energy of individual particles. Such a beam might have an very low intensity, or could be strong enough to be used as a weapon (that's a function of both wattage and diameter). A particle beam can cause either chemical or atomic changes in your lunch (i.e. it could conceivably make it radioactive).

Nope. Lasers are just monochromatic, polarized light, meaning they're beams of photons with nearly the same energy that are all travelling in the same direction. 300MeV is actually really high for a laser; after a little algebra, the wavelength of a laser with that energy is 4.13e-6 nanometers. Most lasers that I know of are visible light or infrared, but light with a wavelength on the order of 10^-6 nm (10^-15 m) is high on the gamma side of the spectrum.

Don't forget all of the other stuff you get from spalling, like high energy X-rays. Actually, at 300MeV, I'd wager on getting a fairly decent gamma ray beam. Without a purpose built collimator, I'd guess that there'd be a good amount of "spray" all over the place. So you'd probably get a hole in a radioactive sandwich, plus a good dose of radiation just for standing nearby. Yes, a healthy dose life-giving radiation [nukees.com].

Remember, the Therac-25 system was quite lethal when it malfunctioned, and it "only" used a 25 MeV beam. 300MeV is a LOT of punch per particle, and if the intensity is high enough all sorts of nasty things will happen.

You lost me there -- by what process? For a z=1 particle at 300MeV/n kinetic energy, the stopping power [sgeier.net] of dry air is about ~3.1 MeV/(g/cm^2) - so that's pretty much transparent. You don't get much energy loss until you hit someone or something. (For Lung tissue I get ~3.5MeV/(g/cm^2), so taking human density to be about ~1, you'd deposit almost half the energy of the particle during penetration of a body (say 30 cm thick))

Not quite, you forgot the flux. 300MeV is the energy per electron so you meant ~4e-11 J/electron. I did not RTFA, but I'm guessing the accelerator produced more than one electron. Also, don't forget, luminosity is also an important way to factor the problem --- electrons/area/sec. That being said, I'd be more concerned about the safety of the lasers they must be using to pump the system.

300 MeV may be 4e-11 J, but that's not the relevant figure. 300 MeV refers to the energy of a single electron in the beam. The beam itself, however, contains many, many electrons, not to mention the energy in the lasers and plasma producing the beam.

They don't mention the potential for experiments like 'what happens if I put my lunch in front of a 300 megaelectronvolt beam?

Some egghead before or during World War II had an egg in his pocket when working around microwave beams when the egg decided to go pop. The device is called a microwave oven and sits on the kitchen counter. I got mine for free when I signed for a one-year lease on my apartment.:P

And don't use the term 'egghead'. It's origin is Nazi brown-shirts referring to how the skulls of intellectuals shatter when they hit the ground. (Or something equally violent.) We have enough anti-intellectualism in this country already.

That's not true. The term dates back to the first decade of the 20th C. as slang for "bald". Chicago newspapermen picked up on the word and started using it to mean someone with intellectual pretensions and the term gained widespread popularization in 1952 when New York Herald Tribune columnist Stewart Alsop used it to refer to the presidential campaign of Adlai Stevenson.

BTW, don't use the term 'egghead'. That anti-intellectual term comes from Nazi brownshirts referring to how easily intellectual's heads shattered, or something equally violent. We have enough anti-intellectualism in this country already. Just look at those damn Geico commercials.

(Seriously. The 'modern' humans are assholes who can mock or outshout the cavemen but that's all... and don't feel any shame about it. The 'cavemen' ar

Maybe you need to check your facts regarding egghead [etymonline.com] since it appears to be American slang. Not unless you were trying to indirectly suggest I'm a Nazi sympathizer. There's enough anti-intellectuals (or people who don't know there facts) in this country.

fortunately it's NOT a proton pack. i say fortunately since the proton pack's inventor is quoted as saying "the proton pack is not a toy" whereas this device is clearly intended for entertainment purposes.

LCDs are making them obsolete, but CRTs (which we all know and loved) work by accelerating electrons to a few keV. The electrons are moving at a not insignificant hunk of the speed of light and produce X-rays as they slam into the front of the tube.

Next time you're sitting in front of one, remember that there's an unlicensed particle accelerator a couple of feet from your brain.